Cytological responses induced by five phytopathogenic fungi in a nonhost plant, Phaseolus vulgaris

1986 ◽  
Vol 64 (3) ◽  
pp. 648-657 ◽  
Author(s):  
Myriam R. Fernandez ◽  
Michèle C. Heath
Keyword(s):  
Phenolic Compounds ◽  
Phaseolus Vulgaris ◽  
Fungal Growth ◽  
Phytopathogenic Fungi ◽  
French Bean ◽  
Mesophyll Cells ◽  
Fresh Tissue ◽  
Susceptible Host ◽  
Nonhost Plant ◽  
Blue Reaction

Responses of the French bean plant (Phaseolus vulgaris L. cv. Pinto) to the nonpathogenic fungi Helminthosporium maydis Nisikado and Miyake (perfect stage Cochliobolus heterostrophus (Drechsler) Drechsler), Stemphylium sarcinaeforme (Cav.) Wiltish., S. botryosum Wallr., Cladosporium fulvum Cooke, and Uromyces vignae Barcl. were examined by cytological and histochemical techniques. All fungi penetrated bean leaves through stomata, and elicited similar modifications in guard and mesophyll cells. Responses involving cell contents were collapse, browning, autofluorescence, and a toluidine blue reaction indicative of the presence of phenolic compounds. Responses associated with cell walls were yellowing, autofluorescence, staining for phenolic compounds, and deposition of callose and of noncallosic, refractive material. In some of the interactions, decolorization and clearing of the tissue for light microscopy induced changes in the frequencies of autofluorescence of cell contents and walls when compared with those observed in fresh tissue. Despite the general similarity of responses elicited by each fungus, striking variations were found among fungi in the percentage of infection sites showing a particular response. For some responses, this variation seemed to be related to the type of interaction each of the fungi has with its susceptible host. It is suggested that even in nonhost plants, the nature and activities of the fungus determine the frequency and extent of the plant's responses. Also, it seems unlikely that all of these responses are involved in the cessation of fungal growth.

scholarly journals Characterization of Nonhost Resistance of Arabidopsis to the Asian Soybean Rust

2008 ◽  
Vol 21 (11) ◽  
pp. 1421-1430 ◽  
Author(s):  
Marco Loehrer ◽  
Caspar Langenbach ◽  
Katharina Goellner ◽  
Uwe Conrath ◽  
Ulrich Schaffrath
Keyword(s):  
Cell Death ◽  
Epidermal Cell ◽  
Fungal Growth ◽  
Soybean Rust ◽  
Nonhost Resistance ◽  
Mesophyll Cells ◽  
Nonhost Plant ◽  
Asian Soybean Rust ◽  
Successful Establishment

Asian soybean rust (ASR), caused by Phakopsora pachyrhizi, is a devastating disease of soybean. We report the use of the nonhost plant Arabidopsis thaliana to identify the genetic basis of resistance to P. pachyrhizi. Upon attack by P. pachyrhizi, epidermal cells of wild-type Arabidopsis accumulated H2O2, which likely orchestrates the frequently observed epidermal cell death. However, even when epidermal cell death occurred, fungal hyphae grew on and infection was terminated at the mesophyll boundary. These events were associated with expression of PDF1.2, suggesting that P. pachyrhizi, an ostensible biotroph, mimics aspects of a necrotroph. Extensive colonization of the mesophyll occurred in Arabidopsis pen mutants with defective penetration resistance. Although haustoria were found occasionally in mesophyll cells, the successful establishment of biotrophy failed, as evidenced by the cessation of fungal growth. Double mutants affected in either jasmonic acid or salicylic acid signaling in the pen3-1 background revealed the involvement of both pathways in nonhost resistance (NHR) of Arabidopsis to P. pachyrhizi. Interestingly, expression of AtNHL10, a gene that is expressed in tissue undergoing the hypersensitive response, was only triggered in infected pen3-1 mutants. Thus, a suppression of P. pachyrhizi–derived effectors by PEN3 can be inferred. Our results demonstrate that Arabidopsis can be used to study mechanisms of NHR to ASR.

Interactions of the nonhost French bean plant (Phaseolus vulgaris) with parasitic and saprophytic fungi. III. Cytologically detectable responses

1989 ◽  
Vol 67 (3) ◽  
pp. 676-686 ◽  
Author(s):  
Myriam R. Fernandez ◽  
Michèle C. Heath
Keyword(s):  
Cell Wall ◽  
Phaseolus Vulgaris ◽  
General Feature ◽  
Fungal Spores ◽  
French Bean ◽  
Cell Necrosis ◽  
Phaseolus Vulgaris L ◽  
Fungal Cell ◽  
Parasitic Fungi ◽  
Nonhost Plant

Cytologically detectable responses of the nonhost French bean (Phaseolus vulgaris L. cv. Pinto) to saprophytic and parasitic fungi were examined when fungal spores were introduced into heated or unheated leaves via wounds or by injection. Although similar types of responses were observed in interactions with all the fungi, some of these responses were characteristic of each group (saprophytes vs. parasites) in the frequency and (or) extent with which they were elicited. Differences in responses between and within each of these groups of fungi were more related to their degree of adaptation for parasitism than to their taxonomic relationships. Certain responses that were typically elicited by the saprophytes occurred to a lesser extent in tissue responding to the parasites, suggesting that the ability to not trigger, or suppress, these responses may be a general feature of parasitic fungi. None of the fungi elicited significant levels of plant cell necrosis, and for two of the saprophytes, dead spores elicited a lower frequency of responses than live ones. The data indicate that many of the responses of a nonhost plant to living fungi may be the result of reactions to fungal activity rather than to constitutive recognition molecules such as components of the fungal cell wall.

Interactions of the nonhost French bean plant (Phaseolus vulgaris) with parasitic and saprophytic fungi. I. Fungal development on and in killed, untreated, heat-treated, or blasticidin S treated leaves

1989 ◽  
Vol 67 (3) ◽  
pp. 661-669 ◽  
Author(s):  
Myriam R. Fernandez ◽  
Michèle C. Heath
Keyword(s):  
Phaseolus Vulgaris ◽  
Fungal Growth ◽  
French Bean ◽  
Phaseolus Vulgaris L ◽  
Subsequent Growth ◽  
Parasitic Fungi ◽  
Heat Treated ◽  
Leaf Resistance ◽  
Blasticidin S ◽  
Bean Leaves

Germination, penetration, and subsequent growth of four saprophytic and five parasitic fungi nonpathogenic on French bean (Phaseolus vulgaris L. cv. Pinto) were examined on, or in, killed, untreated, and heat-treated or blasticidin S treated leaves in the presence (saprophytes only) or absence of additional nutrients. The saprophytes required either an external supply of nutrients or a diffusate from autoclaved leaves to germinate, and they subsequently did not attempt to penetrate untreated or heat-treated living leaves. In contrast, the parasites germinated well, and penetrated untreated tissue almost exclusively through stomata. For some parasites, preinoculation heat treatment increased the incidence of direct penetration and the degree of fungal growth in the tissue. The saprophytes and nonbiotrophic parasites all penetrated and grew well in leaves that had been killed by autoclaving or freezing. The data suggest that living, intact bean leaves are resistant to the fungal saprophytes tested because these fungi lack pathogenicity factors necessary for germination on, and penetration of, the leaf. Resistance to the parasites, in contrast, appears to reside in heat-sensitive and heat- or blasticidin S insensitive defenses in the leaf that may differ with the fungus.

scholarly journals Light and CO2 Modulate the Accumulation and Localization of Phenolic Compounds in Barley Leaves

Antioxidants ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 385
Author(s):  
Lena Hunt ◽  
Karel Klem ◽  
Zuzana Lhotáková ◽  
Stanislav Vosolsobě ◽  
Michal Oravec ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Phenolic Compounds ◽  
Co2 Concentration ◽  
Environmental Stressors ◽  
Low Light ◽  
Mesophyll Cells ◽  
Stress Prevention ◽  
Tolerant Variety ◽  
Barley Leaves

Barley (Hordeum vulgare) accumulates phenolic compounds (PhCs), which play a key role in plant defense against environmental stressors as antioxidants or UV screening compounds. The influence of light and atmospheric CO2 concentration ([CO2]) on the accumulation and localization of PhCs in barley leaves was examined for two varieties with different tolerances to oxidative stress. PhC localization was visualized in vivo using fluorescence microscopy. Close relationships were found between fluorescence-determined localization of PhCs in barley leaves and PhC content estimated using liquid chromatography coupled with mass spectroscopy detection. Light intensity had the strongest effect on the accumulation of PhCs, but the total PhC content was similar at elevated [CO2], minimizing the differences between high and low light. PhCs localized preferentially near the surfaces of leaves, but under low light, an increasing allocation of PhCs in deeper mesophyll layers was observed. The PhC profile was significantly different between barley varieties. The relatively tolerant variety accumulated significantly more hydroxycinnamic acids, indicating that these PhCs may play a more prominent role in oxidative stress prevention. Our research presents novel evidence that [CO2] modulates the accumulation of PhCs in barley leaves. Mesophyll cells, rather than epidermal cells, were most responsive to environmental stimuli in terms of PhC accumulation.

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